import java.util.Scanner;

public class DigitExtractorDriver {

    public static void main(String[] args) {
        DigitExtractor testObj = new DigitExtractor();

        Scanner input = new Scanner(System.in);
        System.out.print("Enter a number (0 - 9999): ");
        String userNumber = input.nextLine();

        System.out.println("Options:");
        System.out.println("1) Ones");
        System.out.println("2) Tens");
        System.out.println("3) Hundreds");
        System.out.println("4) Thousands");
        System.out.println("5) Quit");

        System.out.print("\nWhich option?: ");
        int whatOption = Integer.parseInt(input.nextLine());

        if (whatOption == 5) {
            System.exit(0);
        }

        else if (whatOption == 4) {
            System.out.println(testObj.getThousand());
        }

        else if (whatOption == 3) {
            System.out.println(testObj.getHundred());
        }

        else if (whatOption == 2) {
            System.out.println(testObj.getTen());
        }

        else if (whatOption == 1) {
            System.out.println(testObj.getOne());
        }
    }
}

/////////////////////////////////////////////////////////////////////////////////////////////////////

public class DigitExtractor {

    private String userNumber;
    private String thousands;
    private String hundreds;
    private String tens;
    private String ones;

    // default constructor, setting up just in case nothing is entered
    // also covers if user picks thousands and the number is like... 364
    public DigitExtractor() {
        thousands = "0";
        hundreds = "0";
        tens = "0";
        ones = "0";
    }

    // normal constructor, use if user enters a string
    public DigitExtractor(String n) {
        userNumber = n;
    }

    /***** Getters for each place, if not there return "0" *****/
    public String getThousand() { // 1000
        if (userNumber.length() == 4)
            return userNumber.substring(0, 1);

        else
            return thousands;
    }

    public String getHundred() { // 0100
        if (userNumber.length() == 4)
            return userNumber.substring(1, 2);

        else if (userNumber.length() == 3)
            return userNumber.substring(0, 1);

        else
            return hundreds;
    }

    public String getTen() { // 0010
        if (userNumber.length() == 4)
            return userNumber.substring(2, 3);

        else if (userNumber.length() == 3)
            return userNumber.substring(1, 2);

        else if (userNumber.length() == 2)
            return userNumber.substring(0, 1);

        else
            return tens;
    }

    public String getOne() { // 0001
        if (userNumber.length() == 4)
            return userNumber.substring(3);

        else if (userNumber.length() == 3)
            return userNumber.substring(2);

        else if (userNumber.length() == 2)
            return userNumber.substring(1);

        else if (userNumber.length() == 1)
            return userNumber;

        else // maybe someone will not type -anything?-
            return ones;
    }

}